RFE: update tab name color based on activity

[aristeu]

Hi,
I have just a few DMs and channels I care about and it'd be useful to have some indication if they have new messages, mentions or something of the sort. That way I don't need from time to iterate through them to see if there're new messages.
I started looking at the code but I never did anything serious with rust, so it'll be a while.
Thanks